SRN Blog

On Sunday 8th October we lost a great champion for Australia’s aquatic environment with the passing of Professor Arthur McComb. Arthur has been instrumental in the growth of aquatic ecosystem science in Australia. The underlying theme of Arthur’s research was to understand the fundamental processes that control plant biomass in aquatic systems and the place of primary producers in the functioning of whole ecosystems. His work is of considerable management significance, especially in relation to the effects of nutrients from catchments into receiving waters.

Arthur McComb was born in Melbourne, on 9th December 1936, and graduated with both a BSc and MSc from the University of Melbourne in 1959. He then undertook his PhD at the University of Cambridge, graduating in 1962. Arthur was an associate professor at The University of Western Australia from 1963 until 1988, and full professor at Murdoch University until his retirement in 1996. He was elected to the Australian Academy of Science on 27th April 1996, was awarded the Kelvin Medal of the Royal Society of Western Australia in 1997, the Prime Minister’s Centennial medal for environmental science in 2001, the Australian Marine Science Association Silver Jubilee Award in 2002, and a DSc from Murdoch University in 2007.

Arthur’s legacy will live on through his writings and his students. Arthur has published seminal papers in nearshore systems, estuaries and wetlands. Arthur has written or edited 9 books, including volumes on seagrasses, Australian wetlands, and eutrophic shallow estuaries and lagoons. Over 30 students have completed their PhD’s under his supervision, 3 of whom hold chairs, 2 of them at European universities. His former students are spread throughout Australian science in universities, state government departments and consulting firms, confirming his influence on driving our understanding and management of marine, estuarine and freshwater systems.

Many of us know when pollen is in the air – its allergy season. But have you ever thought about what happens underwater? What do the marine flowering plants do with their pollen? Put your head under water in the middle of winter and have a look!

The cooling water temperatures in the southern hemisphere trigger mass flowering events in the Posidonia meadows. The flowering stems of the ribbon weed Posidonia australis – a long-lived, slow growing seagrass endemic to temperate Australian coastal waters – proudly displays its flowers with bright red anthers (Fig. 1 and 2) in or above the leaf canopy. The flowers are monoecious, containing both male (anthers) and female (stigma) parts. The opportunity for self pollination is reduced by having anthers release pollen before the stigmas become receptive.

Flowering stems were collected during a field trip to Rottnest Island, Western Australia. They were brought back to the laboratory for photographing. The flowers were kept in the fridge, but continued to mature and released their pollen. This video captures the exact moment of pollen release – something that has never been seen before. Elongated sticky pollen capsules are violently catapulted into the water, free of the leaves. The odds of a pollen grain actually coming into contact with a receptive stigma from another plant seem very low. However, it happens often enough, in fact every time a new seed is produced.

This video captures the pollen release from the anthers.

Seagrass pollen is highly modified for moving around in the water. The pollen grains are small, elongated and very difficult to see with the naked eye. They are close to invisible in the water column. The use of genetic markers to identify paternity of seeds (pollen donor plant) demonstrates pollen is mixing well and capable of moving 10’s to 100’s of metres (Sinclair et al. 2014). Seed production is extremely prolific in the seagrass meadows within the Perth metropolitan waters, but highly variable among meadows across Australia.